This invention relates to a fuel delivery rail assembly for an internal combustion engine, especially for an automotive engine, equipped with an electronic fuel injection system. The fuel delivery rail assembly delivers pressurized fuel supplied from a fuel pump toward intake passages or chambers via associated fuel injectors. The assembly is used to simplify installation of the fuel injectors and the fuel supply passages on the engine. In particular, this invention relates to sectional constructions of a fuel conduit (fuel rail) having a fuel passage therein and connecting constructions between the conduit and sockets for receiving fuel injectors.
Fuel delivery rails are popularly used for electronic fuel injection systems of gasoline engines. There are two types of fuel delivery rails; one is a return type having a return pipe and another is a returnless (non-return) type. In the return type, fuel is delivered from a conduit having a fuel passage therein to fuel injectors via cylindrical sockets and then residual fuel goes back to a fuel tank via the return pipe. Recently, for economical reasons, use of the returnless type is increasing and new problems are arising therefrom. That is, due to pressure pulsations and shock waves which are caused by reciprocal movements of a fuel pump (plunger pump) and injector spools, the fuel delivery rail and its attachments are vibrated thereby emitting uncomfortable noise.
Japanese unexamined patent publication No. Hei 11-2164 entitled xe2x80x9ca fuel deliveryxe2x80x9d refers to this problem and discloses a method of manufacturing the fuel delivery body by a steel press process for lowering the co-vibrating rotation caused by the pressure pulsation below the idling rotation and thereby limiting the rigidity and contents of the delivery body within a preselected range. However, in view of the fact that delivery bodies are ordinarily formed by a steel pipe having a circular section or rectangular section, it is rather difficult to adopt the method from the view points of specifications, strength or cost of the engine.
Japanese examined patent publication No. Hei 3-62904 entitled xe2x80x9ca fuel rail for an internal combustion enginexe2x80x9d refers to an injector lapping noise and discloses a construction of diaphragm which divides an interior of the conduit into a socket side and a tube side thereby absorbing pressure pulsations and injector residual actions by its flexibility. However, in order to arrange the flexible diaphragm within the longitudinal direction of the conduit, seal members and complex constructions become necessary, so that overall configurations are relatively restricted. As the results, there are defects that it cannot be applied to miscellaneous specifications of many types of engines.
Japanese unexamined patent publication No. Sho 60-240867 entitled xe2x80x9ca fuel supply conduit for a fuel injector of an internal combustion enginexe2x80x9d discloses a construction that at least one wall of a fuel supply conduit is comprised of a flexible wall so as to dampen fuel pressure pulsations, and the flexible wall is fixed to a rigid wall. However, since the flexible wall is fixed to the rigid wall, its flexibility is not sufficient for obtaining preferable dampening results.
It is an object of the present invention to provide a fuel delivery rail assembly which can reduce the pressure fluctuations within the fuel passages caused by fuel injections, and also to reduce the vibrations caused by fuel reflecting waves (shock waves), to thereby eliminate emission of uncomfortable noise and miscellaneous defects.
A conventional type of fuel delivery rail assembly comprises an elongate conduit having a longitudinal fuel passage therein, a fuel inlet pipe fixed to an end or a side of the conduit, and a plurality of sockets vertically fixed to the conduit adapted to communicate with the fuel passage and so formed as to receive tips of fuel injectors at their open ends.
According to the characteristics of the invention, outer walls of the fuel conduit include at least one flat or arcuate (arched) flexible first absorbing surface. The first absorbing surface is smoothly and integrally connected to an arcuate second absorbing surface. The first absorbing surface or the second absorbing surface faces fuel inlet ports of sockets, which are adapted to receive tips of fuel injectors. Thus, fuel pressure pulsations and shock waves are reduced by abrupt enlargements (spatial expansions) of fuel passages and bendings of the absorbing surfaces.
Several embodiments of the invention are exemplified as follows:
(A) Each section of the conduit is formed in a flat configuration comprised of flat portions and arcuate portions.
(B) Each section of the conduit is formed in a telephone receiver configuration.
(C) Each section of the conduit is formed in a character xe2x80x9cTxe2x80x9d configuration.
(D) Each section of the conduit is formed in a corrugation.
(E) Each section of the conduit is formed in a dumbbell configuration.
(F) Each section of the conduit is formed in a reverse eye mask configuration.
(G) The second absorbing surface is an arcuate flexible end cap fixed to a longitudinal end of the conduit.
As the results of the above constructions of the invention, in a fuel delivery rail assembly having a fuel conduit made by steel, stainless steel or press materials, it has been found that it becomes possible to eliminate the emission of uncomfortable noise due to the vibration and pressure pulsations which are caused by the reflecting waves of injections and lack of dampening performance of the conduit.
In a theoretical principle, when shock waves produced by the fuel injections flow into the fuel inlet of the sockets or flow away therefrom by momentary back streams, flexible absorbing surfaces absorb the shock and pressure pulsations. In addition, when thin plates having small spring constant are deflected and deformed, the space of contents varies, namely expands or shrinks, thereby absorbing pressure fluctuations.
In a preferred embodiment, an inner end of the fuel inlet pipe terminates and opens near the center of the longitudinal conduit. This position is adapted to obtain maximum deflections of the conduit, whereby deflections of the absorbing surfaces are increased so as to enhance shock absorbing performance. However, the position is preferably offset from the center of the socket in order to avoid direct transmission of fuel pressure pulsations.
In this invention, thickness of each wall of the conduit, ratio of the horizontal size to the vertical size, and the range of clearance between the fuel inlet of the socket and its confronting surface are preferably defined by experiments or calculations such that, especially during idling of the engine, the vibrations and pressure pulsations are minimized.
Since the present invention is directed essentially to the sectional construction of the conduit and connecting construction of the conduit and the sockets, interchangeability with the prior fuel delivery rails are maintained as far as the mounting dimensions are kept constant.
Other features and advantages of the invention will become apparent from descriptions of the embodiments, when taken in conjunction with the drawings, in which, like reference numerals refer to like elements in the several views.